Five Oh B Posted November 6, 2006 Report Share Posted November 6, 2006 OK, so I always change the gears in all of my muscle cars for better acceleration. Used to be that you had to, as the factory always put lame gears in for the sake of economy (and/or lack of overdrive). I went from 3.23's to 3.90's in my '68 GTO, 2.73's to 3.73's in my '89 Mustang 5.0L, 3.08's to 4.10's in my '93 T-Bird, etc. It always perked up the acceleration and showed great improvements on my timeslips at the dragstrip. Then, my '03 Mach 1 worked out differently. Factory 3.55's were good for a best 1/4 mile ET of 13.01 (on drag radials). Swapped in 4.30's expecting easy high 12's. Best ET with the 4.30's and the same drag radials was 13.02. The only improvement was trap speed. Typical trap speed with the 3.55's was 102-103 mph, with the occasionaly (but rare) 104+ mph trap speed. With the 4.30's, almost every run was trappin' at 105+ mph. Sixty foot times were the same regardless of gears - typically 1.8's with a 1.79 best for both gear sets. So now I'm unsure whether the 4.10 gears I ordered for my 07 GT will actually do any good. It's a 5-speed automatic coupe, so 1st gear is already pretty low, but I'm really hoping that the 4.10's will really help the launch at the track. Anybody here have an automatic 2005-7 GT with 4.10's (or even 3.73's, 3.90's, or 4.30's) that can relate any hard numbers from their 1/4 mile timeslips? Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 6, 2006 Report Share Posted November 6, 2006 Now I'm confused. Why do you think the gear swap in the Mach didn't make much difference? I thought the rubric was to go through the traps at redline - and whatever gear that took would result in the lowest ET. ?? I'm not an engineer - but I've always felt that the lower gears would get you "there" quicker - the only downside was top end loss. (and I don't need a 160 top end) Link to comment Share on other sites More sharing options...
Five Oh B Posted November 6, 2006 Author Report Share Posted November 6, 2006 Bryan, I'm confused, as well. I think the Mach 1 was actually engineered with the optimum gears from the factory - not just the 3.55 cogs in the differential, but the corresponding transmission ratios, too. I picked 4.30's for the Mach 1 to get it to maximize 4th gear to near redline (as you pointed out) with a little margin left over in case any future mods brought the 1/4 mile speed up. I did the same thing with the 4.10's for the 07 GT. I calculated what gears I would need to be near redline in drive (4th gear) at the end of the 1/4 mile, allowing for a little margin for future mods. The gearing would have been 4.00, so the closest gearset was either 3.90 or 4.10, with 4.10's being easier to find/buy. I really hope the 4.10's will actually do something performance-wise. More gear always used to help, but the Mach 1 left me speechless. Maybe 4.30's were overkill in that car? I do know that most magazine tests of the GT automatics are in the 13.6 to 14.0 range for the 1/4 mile at about 99-100 mph stock. MM&FF recently tested a GT automatic for the "12's or Bust" article that had 4.10's, 3000 rpm stall converter, C&L CAI, and DiabloSport Predator tune. That car went 12.89 at 106.5 with just those mods. I will have added a CAI by the time the track opens (likely the WMS or C&L), and I feel comfortable with the factory torque converter (stalls at 2500 rpms currently), so my car will be nearly the same as the MM&FF car. Even low 13's at 104+ would please me as being about the same as my Mach 1. A couple other minor tweaks and regular high 12's would be reasonable. Any cost-effective suggestions? I'm a working guy on a budget, so superchargers and engine rebuilds are out. Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 6, 2006 Report Share Posted November 6, 2006 Suggestions? From me? You're funny! Man - you have more track time than I have Visa bills! Sounds like you're doing what you can. It is what it is! I'm not an auto guy - but is it worth researching what might be done to the trans? Or - lose some weight! Link to comment Share on other sites More sharing options...
Five Oh B Posted November 7, 2006 Author Report Share Posted November 7, 2006 Point well taken, Bryan. I signed up for Jenny Craig today after reading your suggestion about losing weight. If Kirsty Alley can do it, I can too. I feel a new reality show coming soon: "Fat Drag Racer" starring Five Oh B. Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 7, 2006 Report Share Posted November 7, 2006 Sorry - I meant...... Link to comment Share on other sites More sharing options...
Five Oh B Posted November 7, 2006 Author Report Share Posted November 7, 2006 Bryan, just messin' with ya! I'm 5'7" and 165 lbs. I knew what you meant. The S197's are fat pigs, but we still love them anyway! My 2000 Mustang GT 5-speed coupe weighed 3180 lbs. My 2003 Mach 1 5-speed weighed 3380 lbs. My 2007 GT auto coupe weighs 3540 lbs. All measurements taken at the same truck scales and each car had 1/4 tank gas with nobody in the car. I'll have to research some lightweight goodies for my draft horse so it'll become a quarter horse. Link to comment Share on other sites More sharing options...
Five Oh B Posted November 9, 2006 Author Report Share Posted November 9, 2006 The 4.10's arrived from Holcomb Motorsports the other day. I have an appointment for next Tuesday for the install. The TSB for the noisy differential clutch packs is being done at the same time. Hopefully, I'll have the car back Tuesday evening or Wedesday morning worst case scenario. The same guy that installed the 4.30's in my Mach 1 is doing the 4.10's in my GT. Awesome tech who does it right the first time (seems to be so rare these days). This will actually make 3 cars of mine that our shop has done gear swaps on. The 3rd one was my '93 T-Bird 5.0L LX that they installed a traction-lok carrier and 4.10 gears in. That car's 1/4 mile ET improved .8 second with just the gear swap, but it started life with 3.08 gears and an open diff. On a side note, it just kills me how much disparity there is in price quotes out there to install a new ring & pinion. Even though I was pretty certain I'd have our dealership do the install for me, I had to check around again just to sleep better at night about the money. I'm being charged under $300 by our shop for the labor (at a discounted employee rate). A very well-known local shop that does only ring & pinion work quoted about $380 for the labor. I paid $220 for the parts, so that's under $500 total using our shop, or $600 using the ring & pinion place. So far, so good. I asked a specialty Mustang shop, and they quoted $700 parts & labor. And a well-respected hot rod shop in the area quoted about $1200 part & labor. All quotes were based on FRPP 4.10 gears, so the only variable is how much they think they labor is worth. Also, I have a hp formula that predicts 1/4 mile trap speed based on the weight of the car, which in turn can be used to predict ET's, that I've used over the years on a variety of my drag cars that is very, very accurate. Assuming for decent traction, it predicts that my GT should run the 1/4 mile in the 13.20's at 102+ mph with the Predator Tune in the car (20 extra hp) and the 4.10 gears. That would be a nice improvement over the stock tests for GT automatics which have typically been in the high 13's @ 99 mph. Kind of wish I could have gotten to the track before mods to get a baseline run for comparision sake. Oh well! Link to comment Share on other sites More sharing options...
kraegar Posted November 9, 2006 Report Share Posted November 9, 2006 On a side note, it just kills me how much disparity there is in price quotes out there to install a new ring & pinion I've found this to be true as well - some shops seem to think their work is worth far more, when in reality, it's not usually the case. Finding a shop with a good rep, good value, that stands by their work is a must. You're lucky you work for a dealer, and it's easy for you The 4x4 shop I used to take my '80 cj-7 closed a few years back... the only shop I'd ever taken it to for anything. It was a real pain to find anyone who knew anything about a 304 v-8, let alone had "sane" pricing for working on it. I finally got lucky when two local gear-heads opened a shop just down the block from my house. If it weren't for that shop, I think I'd still be paying through the nose for even the smallest work. (places kept freaking out about working on that beast). - Tony Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 9, 2006 Report Share Posted November 9, 2006 Thanks, Fiveoh - how about running my numbers through your equation?! My tech thinks the car should run upper 12's. Link to comment Share on other sites More sharing options...
90GT Posted November 10, 2006 Report Share Posted November 10, 2006 Thanks, Fiveoh - how about running my numbers through your equation?! My tech thinks the car should run upper 12's. Only high 12's??!! I would think that if your car makes the 370 rwhp like your tech says it should plus the 4:10's you should be in the mid 12's. Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 10, 2006 Report Share Posted November 10, 2006 Time will tell. And so will the slip. Link to comment Share on other sites More sharing options...
ratnacage Posted November 10, 2006 Report Share Posted November 10, 2006 B)--><div class='quotetop'>QUOTE(Five Oh B @ Nov 9 2006, 01:29 PM) 57870[/snapback]</div><div class='quotemain'><!--quotec--> Also, I have a hp formula that predicts 1/4 mile trap speed based on the weight of the car, which in turn can be used to predict ET's, that I've used over the years on a variety of my drag cars that is very, very accurate. Assuming for decent traction, it predicts that my GT should run the 1/4 mile in the 13.20's at 102+ mph with the Predator Tune in the car (20 extra hp) and the 4.10 gears. That would be a nice improvement over the stock tests for GT automatics which have typically been in the high 13's @ 99 mph. Kind of wish I could have gotten to the track before mods to get a baseline run for comparision sake. Oh well! I remember back in the days before the internet, Jacobs had a book that contained formulas like that. Now you can just google it: http://www.nightrider.com/biketech/calc_formulas_page.htm One thing is that whether you are a good driver or just average, trap speed is a great way to determine the effectiveness of mods. You can have a crappy ET, but the MPH tells the tale. I've gone to the track and had ET's all over the place, but the MPH was always within +/- 1. Link to comment Share on other sites More sharing options...
Five Oh B Posted November 11, 2006 Author Report Share Posted November 11, 2006 Bryan, if your GT puts 370 hp to the ground and we assume the car (with you) weighs 3600 lbs, then you'll finish the 1/4 mile at 114 mph. With perfect traction and awesome driving, this would yield 11.8's in the 1/4 mile. With average traction or average driving, that should yield 12.2's. But, where did the 370 rear wheel hp figure come from? That sounds very optimistic, unless I don't understand all the mods you've done. If it is really 370 hp at the crankshaft, then you'd have about 315 hp at the ground. Based on that scenario, and still assuming 3600 lbs, then you'll finish the 1/4 mile at 108 mph. With perfect traction and awesome driving, this would yield 12.5's in the 1/4 mile. With average traction or average driving, that should yield 12.9's. One thing is that whether you are a good driver or just average, trap speed is a great way to determine the effectiveness of mods. You can have a crappy ET, but the MPH tells the tale. I've gone to the track and had ET's all over the place, but the MPH was always within +/- 1. So true. MPH tells you how much power the car makes. ET tells you how good a driver you are (or how good the traction was/wasn't). Link to comment Share on other sites More sharing options...
Five Oh B Posted November 11, 2006 Author Report Share Posted November 11, 2006 Here’s a couple of handy formulas that may help you guys estimate the horsepower or ¼ mile potential of your car, assuming you know two of the three variables. RWHP = WEIGHT [MPH / 244]^3 MPH = [RWHP / WEIGHT]^.333 * 244 ¼ MILE ET with ideal gearing, traction, driving, etc. = 1350 / MPH ¼ MILE ET with just average gearing, traction, driving, etc. = 1400 / MPH ¼ MILE ET with bad traction, driving, etc. = 1450 / MPH Below are explanations that may be useful in using the formulas above. RWHP = rear wheel horsepower, which is roughly advertised hp at the crank * .85. Therefore, in a 300 hp Mustang GT, you should expect about 255 hp at the ground. (300 * .85). WEIGHT = weight actually going down the ¼ mile track (including car & driver). MPH = trap speed at the end of the ¼ mile. ^3 = cube, or the prior number multiplied by itself 3 times. ^.333 = cubed root of a number. Ask a math buddy if your math skills are rusty. ¼ MILE ET vs MPH math assumes that the better you drive, the better traction you get, and the better suited your car is at drag racing, the lower the product of those two numbers will be and the closer it will be to 1350. The lower the better. If you multiply your ET by your MPH, the product will get higher and higher as your driving gets worse, traction gets worse, etc. I created these formulas myself over the years, but based the hp formula on some old formulas used years ago in HotRod magazine. Grab some 1/4 mile timeslips you have lying around and plug in some numbers (assuming you know how much the car in question weighed for those timeslips). I think you'll find the math very accurate, or at least a very good estimate in lieu of actual dyno testing. Remember, horsepower is a simple mathematical formula of measuring a how long it takes to move a known weight over a known distance. Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 11, 2006 Report Share Posted November 11, 2006 Thanks, Fiveoh - I'm not sure where the 370 number came from. I expect about 325-340 at the wheels. And 12.5's would taste very good! After dyno day - I need to find some cheap 17" rims and buy some Nittos and see if my eye/hand coordination is still worth anything. To be blunt - I'm a little worried about making an ass of myself at the strip. It's been a very long time.... "cubed root" ?? Methinks you forget I teach English..... Link to comment Share on other sites More sharing options...
Five Oh B Posted November 11, 2006 Author Report Share Posted November 11, 2006 Thanks, Fiveoh - I'm not sure where the 370 number came from. I expect about 325-340 at the wheels. And 12.5's would taste very good! After dyno day - I need to find some cheap 17" rims and buy some Nittos and see if my eye/hand coordination is still worth anything. To be blunt - I'm a little worried about making an ass of myself at the strip. It's been a very long time.... "cubed root" ?? Methinks you forget I teach English..... Oh Bryan, I knew you taught English, that's why there was a reference to ask a "math buddy" if your math skills were rusty. I'm a math geek, so I often create formulas or spreadsheets to solve some of life's questions, but I know that not everyone will understand the process that goes into it. If you're going to buy drag radials, here's what I can relate from personal experience: Nitto DR's are a harder compound than the BFG DR's, so the Nitto's will last longer (great if you'll keep them on the car and drive on them a lot), while the BFG's will be stickier at the track (with a shorter life if you use them on the street). As I (and presumably you) will use the big/fancy wheels on the street, and the 17's with DR's just on track days, then I would recommend the stickier BFG's over the Nitto's. With all the newfound power in your pony, you're gonna need the extra traction! I recalculated the math for your car, assuming 325 RWHP and 3,600 lbs with you in the car. You should be able to top 109 mph at the end of the 1/4 mile regardless of how bad you launch. The ET is the telltale sign of your skill and traction. Drive poorly and spin the tires hard, and you'll run mid 13's. Do an average job, and still spin a little too much and low 13's are yours. Do some practicing, or let me run your car down the track, and your car should net high 12's. Loan your car to John Force and have the DR's nice and sticky and your car will run 12.40's. Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 11, 2006 Report Share Posted November 11, 2006 FiveOh - I really appreciate your time here. Man - I like hearing it from a Source! I wish you were close by - I'd love some in-car lessons. I had one math class out of 60 college courses - one - too - many! Link to comment Share on other sites More sharing options...
Five Oh B Posted November 12, 2006 Author Report Share Posted November 12, 2006 FiveOh - I really appreciate your time here. Man - I like hearing it from a Source! I wish you were close by - I'd love some in-car lessons. I had one math class out of 60 college courses - one - too - many! Well, in-car lessons are fine by me, but I've never taught math in a car before. Physics, maybe, but not math. I had one math class out of 60 college courses - one - too - many! I only had a few English classes in college, so I'm at the opposite end of the spectrum. Lots of technical writing courses to go with all the business classes (finance, economics, banking, statistics, marketing, accounting, Int'l studies, etc.), but little to do with English. I bet I took more Spanish classes than English. Spanish is such a beautiful language that I took 5 years of it between high school and college. Can't carry on a conversation in Spanish to save my soul, but I can read and write it better than the average 10 year old kid from Mexico. Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 12, 2006 Report Share Posted November 12, 2006 Light bulb comes on!! Five oh B's Drag Racing School!! Brilliant! I'm talking about a beginners to intermediate school for those with little experience on the strip. Why not? I'm in for a piece of it. Link to comment Share on other sites More sharing options...
Five Oh B Posted November 12, 2006 Author Report Share Posted November 12, 2006 Five oh B's Drag Racing School!! That's funny, but ironic. A couple guys at www.Mach1Registry.com have given me a ton of crud about jumping ship from the 03 Mach 1 to the 07 GT. Apparently, the new GT's aren't as good a Mustang as the Mach 1's in their opinion and that I made a huge mistake trading the Mach 1 for a "lesser" Mustang. Anyway, they've been heckling me because I'm a "bad" drag racer for not being able to get the Mach 1 to run 12's in the 1/4 mile. Bone stock, with just drag radials it went a best of 13.01 @ 104.5. They seem to think all the Mach 1's run 12's and there's something wrong with my track abilities. But then, you look at the 1/4 mile drag list on that website, and there are dozens and dozens of Mach 1's in the 13's and even some in the 14's. And all of those that were faster than me were modded (many quite heavily). It's nice to see all the mods posted for each car to get an idea of what works and what doesn't. Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 12, 2006 Report Share Posted November 12, 2006 I'm serious about the school. Link to comment Share on other sites More sharing options...
mastersmech1 Posted November 12, 2006 Report Share Posted November 12, 2006 I need all the schooling I can get. You're never too old to learn. :happy feet: Bring it on. Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 12, 2006 Report Share Posted November 12, 2006 See? You've got 2 students already. Link to comment Share on other sites More sharing options...
mastersmech1 Posted November 12, 2006 Report Share Posted November 12, 2006 See? You've got 2 students already. Alright...and i've got two teachers. I expect my grammer and drag racing skills to improve!!! Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 12, 2006 Report Share Posted November 12, 2006 Easy, now, big boy! Let's not expect too much at once! Anybody seen Commander Orf? Link to comment Share on other sites More sharing options...
mastersmech1 Posted November 12, 2006 Report Share Posted November 12, 2006 Easy, now, big boy! Let's not expect too much at once! Anybody seen Commander Orf? Hopefully he's out ripping through those new gears. Can't wait for an update. :hyper: Link to comment Share on other sites More sharing options...
lambbo Posted November 12, 2006 Report Share Posted November 12, 2006 Five Oh B, I finally found the 3.90 for the 8.8. Thanks for the info. Here is the link if anyone is interested. http://www.americanmuscle.com/rearend.html Link to comment Share on other sites More sharing options...
RUFDRAFT Posted November 12, 2006 Report Share Posted November 12, 2006 ?? Gears? He didn't tell me. What did he put in? 3.73's? Link to comment Share on other sites More sharing options...
mastersmech1 Posted November 12, 2006 Report Share Posted November 12, 2006 ?? Gears? He didn't tell me. What did he put in? 3.73's? 10-4 ... when I last heard he hadn't had much windshield time since the install. Link to comment Share on other sites More sharing options...
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